In order to provide close fitting of flat surfaces of various mechanical work pieces, such as mechanical seals, it is desirable to provide a means for testing the flatness of such surfaces without having to rely on the trial and error method of actually installing the work piece in its expected operation to see if it works properly. Quite often the testing of the flat surface is desired to be performed at some distance remote from its intended installation.
The present invention provides a new, improved means and method of testing the flatness of the surface of a work piece, involving the commonly-known "optical flat" technique.